I have a slightly different issue: flashing seem to have worked ok, but I get the screen “SD” with two red lines, even though I have copied the ‘wifi’ folder inside 00system on the SD card.
When I power off / power on, I get 3 to 5 random leds on the GF main display, then after a few seconds the yellow “SD” + 2 red lines appear. After about a minute, I see a reboot (blank screen), then “SD” error screen again.
I checked multiple times the SD card, and everything looks alright. I have the 00system folder with the previous stuff, and the new wifi subfolder with wifi.ini a bunch of bmps and html and subfolders (email, follower, iss, twitter, …)
The /00system/wifi/wifi.ini file has wifi=true, and inifile=false.
Behind the device, on the photon board, I see a blue led (right next to D7) and a white pulsating LED between the RST/SETUP buttons. On the GF board itself, I see the red POWER led on, and the green STATUS led is pulsating fast.